Download Genetic Problem Worksheet

Human Physiology Fall: 2007
Genetic Problems
Answer each of the question below with either the genotype or the probability of the
event occurring. Use the Punnett Square tables provided to solve the problems. The
probabilities will be posted on my homepage.
1. Widow’s Peak is a condition when the hair grows to a point on the forehead.
Widow’s Peak is an autosomal dominant trait. Both Jack and Jill are heterozygous
for widow’s peak. What are the chances that their son John will also have a
widow’s peak?
2. George has attached ear lobes. Attached earlobes are an autsomal recessive trait.
Laura has free ear lobes, but she is heterozygous for this trait. What are the
chances of their child having free earlobes?
3. The trait of being able to “roll your tongue” is an autosomal dominant trait.
Charlie can’t roll his tongue, but his father can. What is Charlie’s father’s
genotype for tongue rolling?
4. The allele for Tay-Sachs is an autosomal recessive trait that results in death
during early childhood. The Tay-Sachs program has enabled Bernie to determine
that he is a carrier and that his wife is not. What are the chances they could have
a child with Tay-Sachs?
5. Persons who are heterozygous for sickle cell anemia are said to have the sickle
trait (but not the disease). What are the chances that Sam and Ethyl, who both
have the trait, will have a child with the disease of sickle cell?
6. John can roll his tongue, but his mother cannot. John also has attached earlobes.
He meets Marsha, who cannot roll her tongue but has free earlobes. Marsha’s
father, however, has attached earlobes. What are the chances that their child will
have free earlobes and be able to roll its tongue?
7. Jose is homozygous for Huntington’s and heterozygous for cystic fibrosis. HD is
autosomal dominant and CF is autosomal recessive. Elvira is homozygous
normal for Huntington’s but a carrier of cystic fibrosis. What are the chances that
their child has Huntington’s disease but not Cystic Fibrosis?
8. Repeat the same problem of #8 but now have Jose be heterozygous for
Huntington’s disease. Keep everything else the same. What are the chances that
their child has Huntington’s and Cystic Fibrosis?
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9. Fred is type AB and his wife is type O. Type O blood is autosomal recessive.
What is the probability that they have a child with type A blood? With type B
blood? With type O blood?
10. Hemophilia is an X linked trait. If a mother is heterozygous for hemophilia and
father does not have hemophilia, what is the probability that they have a child
with hemophilia?
Frequently encountered genetic terms
Terms related to Inheritance, DNA and Genetics. These terms are frequently used
when discussing the concepts of inheritance and their related problems. Familiarity with
these terms assists in the understanding of the genetic basis of inheritance and solving
genetic based problems.
allele
autosomal
carrier
cell cycle
chromosome
co-dominance
cytokinesis
dihybrid cross
diploid
dominant
gametes
gene
genotype
germ cells
haploid
heterozygous
homologous
homozygous
homozygous dominant
homozygous recessive
karyotype
meiosis
mitosis
non-homologous
phenotype
Punnett Square
recessive
sex-linked
somatic cell
“X”-linked trait
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Punnett Squares
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